1. Field of the Invention
The present invention relate to the cutting and finishing of expansion and construction joints in highway and street concrete curb construction. An expansion joint in concrete curbing is necessary to allow for linear expansion and contraction of the concrete, in order to prevent fragmentation and destruction of the curbing.
2. Related Art
Before the automatic, self-powered slip-form curbing machine, roadside curbing was formed and constructed by hand by skilled technicians. Expansion joints were formed by heading-up or terminating the curb and finishing an interior face of the joint. Then, adjacent that face, the expansion joint material was installed, and construction of the subsequent curb began against that face.
In the current highway and street industry, a compacted-concrete curbing is automatically auger-extruded from a self-propelled, laser-guided curb-paving machine. Such machines have revolutionized curb building except for one crucial aspect: cutting joints. Today, joints are either hand-built per above, or “paved-through” and then saw cut while semi-cured. Saw cutting is typically performed using a diamond blade, which is expensive, and leaves sharp edges that, absent trawled edging, is subject to edge chips.
To date, a master finisher, or concrete mechanic, is still required for constructing expansion joints. The freshly extruded, green concrete curbing must be temporarily destroyed for at least six inches on each side of the designated joint in order to construct the joint, and then rebuild the remainder of the temporarily destroyed curb with un-compacted concrete, thus diminishing cohesive integrity. The finisher must also be mindful that the shelf life of concrete begins expiring upon exiting the concrete plant. The integrity of consolidated, cohesive homogeneity through chemical reaction must be maintained and undisturbed throughout the restored cross-section of the joint until fully cured. The mix must be wet enough to be pliable, while at the same time, stiff enough to maintain the prescribed cross-section profile.
Construction expansion joints can also be cut with a diamond-tipped saw blade. However, good hands-on finishers can build acceptable joints much cheaper than the cost of sawing, but the overall integrity of the product is weakened by re-handling, time-lapse, but mostly by lack of compacted concrete immediate to both interior faces of a joint. A properly functioning mechanical joint is as important to the roadway as is the curb itself.